This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the disclosed methodologies and techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Hydrocarbon reserves are becoming increasingly difficult to locate and access, as the demand for energy grows globally. Typically, various technologies are utilized to collect measurement data and then to model the location of potential hydrocarbon accumulations. The modeling may include factors, such as (1) the generation and expulsion of liquid and/or gaseous hydrocarbons from a source rock, (2) migration of hydrocarbons to an accumulation in a reservoir rock, (3) a trap and a seal to prevent significant leakage of hydrocarbons from the reservoir. The collection of these data may be beneficial in modeling potential locations for subsurface hydrocarbon accumulations.
At present, reflection seismic is the dominant technology for the identification of hydrocarbon accumulations. This technique has been successful in identifying structures that may host hydrocarbon accumulations, and may also be utilized to image the hydrocarbon fluids within subsurface accumulations as direct hydrocarbon indicators (DHIs). However, this technology may lack the required fidelity to provide accurate assessments of the presence and volume of subsurface hydrocarbon accumulations due to poor imaging of the subsurface, particularly with increasing depth where acoustic impedence contrasts that cause DHIs are greatly diminished or absent. Additionally, it is difficult to differentiate the presence and types of hydrocarbons from other fluids in the subsurface by such remote measurements.
Current geophysical, non-seismic hydrocarbon detection technologies, such as potential fields methods like gravity or magnetics or the like, provide coarse geologic subsurface controls by sensing different physical properties of rocks, but lack the fidelity to identify hydrocarbon accumulations. These tools may provide guidance on where in a basin seismic surveys should be conducted, but do not significantly improve the ability to confirm the presence of hydrocarbon seeps or subsurface hydrocarbon accumulations. Other non-seismic hydrocarbon detection technologies may include geological extrapolations of structural or stratigraphic trends that lead to prospective hydrocarbon accumulations, but cannot directly detect these hydrocarbon accumulations. Other techniques may include monitoring hydrocarbon seep locations as an indicator of subsurface hydrocarbon accumulations. However, these techniques are limited as well. For example, satellite and airborne imaging of sea surface slicks, and shipborne multibeam imaging followed by targeted drop core sampling, have been the principal exploration tools used to locate potential seafloor seeps of hydrocarbons as indicators of a working hydrocarbon system in exploration areas. While quite valuable, these technologies have limitations in fidelity, specificity, coverage, and cost.
There are several methods proposed in the art to detect hydrocarbons from an underwater location (e.g., within or at least partially within the body of water). The typical sensors are associated with leak detection. For example, Great Britain Patent No. 2382140 describes a method that involves the use of acoustic or other signal pulses to detect pipeline leakage. As another example, U.S. Pat. No. 7,728,291 describes a method that utilizes fluorescence polarization to detect viscous oil residues. Further, in Shari Dunn-Norman et al, “Reliability of Pressure Signals in Offshore Pipeline Leak Detection”, Final Report to Dept. of the Interior, MMS TA&R Program SOL 1435-01-00-RP-31077, pressure safety low alarms are described as being utilized to detect pipeline leakage. Also, other methods of different hydrocarbon detection technologies may include the use of fluorometric sensors, acoustic sensors, a methane sensor or a temperature sensor mounted on a remotely operated vehicle (ROV) to detect pipeline leakage, as noted by Neptune Oceanographics Ltd (NOL), http://www.offshore-technology.com/contractors/pipeline_inspec/neptune/2011 (visited on Jul. 25, 2012).
While these various different sensors may be utilized, the movement of the sensors typically involves operators and other personnel to control and manage the operation via umbilical cables. For example, certain systems utilize a remotely operated vehicle (ROV) for subsea leak detection. The ROV is equipped with a sensor to detect leaks. Unfortunately, as the ROV has to be manually controlled, a large number of operator hours are required to conduct such a pipeline survey. Another example includes U.S. Pat. No. 4,001,764, which describes the use of a towing and recording boat to pull a SONAR sensor for detection of pipeline leakage. This system requires operators to manage the towing boat and associated equipment.
Also, other technologies may involve the use of vehicles to survey the seabed. For example, U.S. Patent Application No. 20110004367 describes a remotely operated vehicle (ROV), which may be utilized for certain missions. Further, a GOSL publication describes the use of a Marport SQX-1 AUV capable of operating to 500 meters water depth, which may utilize sensors including SONAR. See Geodetic Offshore Service Limited (GOSL) (http://www.goslng.com/marport.asp) (visited on Jul. 25, 2012). However, this reference appears to rely only upon a methane sniffer for leakage detection, which can result in reliability problems due to the lack of additional sensor information. Another reference is Intl Patent Application No. 2012052564. This reference describes an AUV to acquire gravity and magnetic data near the seafloor.
Other examples of academic research are described in Jakuba et al. (2011; Jakuba Michael V, Steinberg D, Pizarro O, Williams S B, Kinsey J C, Yoerger D R, Camilli R. Toward automatic classification of chemical sensor data from autonomous underwater vehicles. AIROS'11—2011 IEEE/RSJ International Conference on Intelligent Robots and Systems: Celebrating 50 Years of Robotics. IEEE International Conference on Intelligent Robots and Systems (2011), pp. 4722-4727, arn: 6048757, 23 refs. CODEN: 85RBAH ISBN: 9781612844541 DOI: 10.1109/IROS.2011.6048757 Published by: Institute of Electrical and Electronics Engineers Inc., 445 Hoes Lane/P.O. Box 1331, Piscataway, N.J. 08855-1331 (US).; Camilli et al. (2010; Camilli, R., Reddy, C. M., Yoerger, D. R., Jakuba, M. V., Kinsey, R. C., McIntyre, C. P., Sylva, S. P., and Maloney, J. V. Tracking Hydrocarbon Plume Transport and Biodegradation at Deepwater Horizon, Science 330 (6001): 201-204; Kinsey et al. (2011; Kinsey J C, Yoerger D R, Camilli R, German C R, Jakuba M V, Fisher C R. Assessing the deepwater horizon oil spill with the sentry autonomous underwater vehicle. IROS'11—2011 IEEE/RSJ International Conference on Intelligent Robots and Systems: Celebrating 50 Years of Robotics. IEEE International Conference on Intelligent Robots and Systems (2011), pp. 261-267, arn: 6048700, 30 refs. CODEN: 85RBAH ISBN: 9781612844541 DOI: 10.1109/IROS.2011.6048700 Published by: Institute of Electrical and Electronics Engineers Inc., 445 Hoes Lane/P.O. Box 1331, Piscataway, N.J. 08855-1331 (US)); Zhang et al. (2011; Zhang Y, McEwen R S, Ryan J P, Bellingham J G, Thomas H, Rienecker E, Thompson C H. A peak-capture algorithm used on an autonomous underwater vehicle in the 2010 Gulf of Mexico oil spill response scientific survey. Journal of Field Robotics (July 2011) Volume 28, Number 4, pp. 484-496, 21 refs. ISSN 1556-4959 E-ISSN: 1556-4967 DOI: 10.1002/rob.20399 Published by: John Wiley and Sons Inc., P.O. Box 18667, Newark, N.J. 07191-8667 (US)) along with Intl. Application Publication No. 2012/052564. Further, other references describe discriminating between thermogenic and biogenic hydrocarbon sources. See, e.g., Sackett W M., Use of Hydrocarbon Sniffing. Offshore Exploration. Journal of Geochemical Exploration, 7:243-254 (1977).
Despite these different technologies, many frontier hydrocarbon exploration ventures result in failures. In particular, these failures are attributed to an inability to fully evaluate, understand, and appropriately risk the hydrocarbon system components, from source to seeps (e.g., source presence and maturity, migration, accumulation and leakage). As a result, an enhancement to the exploration techniques is needed. In particular, a method and system is needed to locate seafloor hydrocarbon seeps accurately and cost-effectively over the basin-to-play scale as a means to enhance basin assessment and to high-grade areas for exploration.